1. Field of the Invention
The present invention relates to a transfer method and a transfer apparatus used in the method, and more particularly, to a transfer method and a transfer apparatus for thermally transferring a luminescent layer of an organic electroluminescence (EL) device.
2. Description of the Related Art
In a full-color display device, organic electroluminescent devices corresponding to colors of R (red), G (green), and B (blue) are arranged on a substrate. In this display device, it is necessary at least to pattern luminescent layers corresponding to the colors in each organic electroluminescent device.
One method for patterning luminescent layers is a transfer method using an energy source (heat source) (thermal transfer method). As a thermal transfer method, for example, Japanese Unexamined Patent Application Publication No. 2004-200170 discloses a contact method in which transfer is performed while a donor substrate and a receptor substrate are in tight contact with each other with a transfer layer therebetween, and Japanese Unexamined Patent Application Publication No. 2004-79540 discloses a separate method in which transfer is performed while a donor substrate and a receptor substrate are separate from each other.
A transfer apparatus used in the thermal transfer method generally includes a vacuum chamber in which transfer operation is performed, and a radiation source that applies a radiant ray so as to apply heat to a donor substrate placed in the vacuum chamber. For example, movable holding members are provided in the vacuum chamber to respectively hold and vertically move a donor substrate and a receptor substrate. The holding member for the donor substrate is disposed above the holding member for the receptor substrate in the vacuum chamber such that the donor substrate and the receptor substrate face each other.
An opening that is one size smaller than the donor substrate is provided at the top of the vacuum chamber, and an airtight seal is provided on the periphery of the opening and on an upper inner wall of the vacuum chamber. The donor substrate closes the opening with the airtight seal therebetween, thereby keeping the vacuum chamber airtight.
The radiation source is disposed above the vacuum chamber to apply heat to the donor substrate. For example, a laser light source is used as a heat source. The laser light source is moved by an XY scanner so that a spot of laser light is scanned.
In order to form a luminescent layer of an organic electroluminescent device in a contact thermal transfer method using the above-described transfer apparatus, a receptor substrate and a donor substrate are put in the vacuum chamber, and are respectively mounted on the corresponding holding members so that an organic layer of the receptor substrate faces a transfer layer of the donor substrate.
Subsequently, the vacuum chamber is closed by blocking the top opening thereof by means of a gate valve from the outside, and the pressure in the vacuum chamber is reduced to that of a vacuum. Then, the holding member for the donor substrate is moved upward so that the donor substrate closes the opening from the inside, and the holding member for the receptor substrate is pushed up to bring the receptor substrate into contact with the donor substrate. When the gate valve is then opened, the upper portion of the vacuum chamber including the donor substrate is pushed from above by the atmospheric pressure, and therefore, the donor substrate is brought into tight contact with the receptor substrate. By scanning a spot of laser light over the donor substrate in this state, the transfer layer is transferred onto a predetermined region of the receptor substrate.
The basic configuration of a transfer apparatus that performs transfer in a separate thermal transfer method is the same as that of the above-described contact thermal transfer apparatus. A donor substrate and a receptor substrate are put in a vacuum chamber so as to face each other with some space therebetween. Then, the interior of the vacuum chamber is evacuated, and laser light is applied onto the donor substrate to transfer a transfer layer from the donor substrate onto the receptor substrate.